1. Field of the Invention
The present invention relates to an optical module and a processing method using the same.
2. Related Background Art
At present, processing technology using laser light is attracting much attention, and demand for laser light sources is increasing in various fields such as machining and medical treatment. In particular, among various laser light sources, a laser light source which is attracting special attention includes a fiber laser light source. An optical fiber which is doped with rare earth elements such as Yb, Er and Tm is used as an optical amplification medium, and therefore light to be amplified is amplified by pumping light and laser oscillation is produced using a resonator structure, thereby generating light having a high output. The advantages of the fiber laser light source are that, since the laser light is confined within the optical fiber, treatment is easy, and since heat radiation properties are good, a large-scale cooling installation is not required.
As an amplification optical fiber, a fiber having a refractive index profile of single-cladding type is used in some cases. This amplification optical fiber of single-cladding type has one core which is doped with a rare earth element, and one cladding which surrounds this core and has a refractive index lower than that of the core. Further, this amplification optical fiber allows the light to be amplified to propagate in a single mode in the core and also allows pumping light to propagate in the core. In the amplification optical fiber, the rare earth element is excited by the pumping light and stimulated emission is caused. At this time, the light to be amplified which propagates through the amplification optical fiber is amplified. The pumping light which is not absorbed by the amplification optical fiber transmits through the amplification optical fiber to the outside (hereinafter, the pumping light which transmits is referred to as transmitting pumping light).
Further, as an amplification optical fiber, an optical fiber having a refractive index profile of double-cladding type is preferably used. The amplification optical fiber of double-cladding type has a core which is doped with rare earth elements, an inner cladding which surrounds the core and has a refractive index lower than that of the core, and an outer cladding which surrounds the inner cladding and has a refractive index lower than that of the inner cladding. Further, the amplification optical fiber allows the light to be amplified to propagate in a single mode in the core and allows the pumping light to propagate in a multimode in the core and the inner cladding. When such an amplification optical fiber of double-cladding type is used, high power pumping light is allowed to propagate in the amplification optical fiber and the light to be amplified can be amplified with a high gain (high-power amplified light is obtained).